First to answer the most FAQ: Brother MFC 4600 (and a few others) is supported by ghostscript hl7x0 driver. Other MFC devices may be supported by PCL or PS drivers.
The goal of the project is to provide support for scanner, fax and other goodies. If all you want is to print then you don't need this.
The project is not actively developed due to the lack of interest. I've got scanner and fax working but it is nowhere near production quality.
If you need more info send me an e-mail.